Two complexes between mono-deprotonated calix[4]arene and Et(3)HN+ are reported. The first, triethylammonium 26,27,28-trihydroxypentacyclo[19.3.1.1(3,7).1(9,13).1(15,19)]octacosa-1(25),3,5,7(28),9,11,13(27),15,17,19(26),21,23-dodecaen-25-olate, C(6)H(16)N+ x C(28)H(23)O(4)-, comprises only the cationic and anionic species, whereas the second, tris(triethylammonium) tris[26,27,28-trihydroxypentacyclo[19.3.1.1(3,7).1(9,13).1(15,19)]octacosa-1(25),3,5,7(28),9,11,13(27),15,17,19(26),21,23-dodecaen-25-olate] acetonitrile solvate, 3C(6)H(16)N+ x 3C(28)H(23)O(4)(-) x C(2)H(3)N, comprises one acetonitrile solvent molecule for three such units. In both cases, the units are stacked in columns so that the ammonium cation is hydrogen bonded to a phenolic or phenolate O atom of one molecule and included in the hydrophobic cavity of another neighbouring calixarene. The short contacts present indicate that cation* * *pi and C-H* * *pi interactions are likely to be involved in the inclusion phenomena.